The present invention relates to a method of producing a phosphor screen of color picture tube, and more particularly to a method of producing a black (light-absorbing) matrix of a color television picture tube, which permits very few defects to develop on the phosphor screen, which enables the manufacturing process to be simplified, and which contributes to reducing the manufacturing cost.
According to methods of manufacturing a black matrix of a color television picture tube that have heretofore been put into practice as disclosed in Japanese Patent Publication No. 218/1971, or in U.S. Pat. No. 3,558,310, a photosensitive material is applied onto the inner surface of a picture tube panel, exposed through a shadow mask, developed to form a desired pattern, and a suspension of light-absorbing material such as graphite is applied onto the whole surface, followed by a treatment with an etching solution consisting of an aqueous solution of hydrogen peroxide, sodium hypochlorite or the like, so that the photosensitive material that is exposed and cured is swollen and eroded. The photosensitive material is then developed again and is eroded, and is peeled off together with the light-absorbing material to form a black matrix pattern composed of the light-absorbing material that was not exposed. Thereafter, phosphor film patterns of green, blue and red are formed on the inner surface of the panel by such methods as a slurry or a dusting method, a film of acrylic resin is formed on the phosphor film patterns of these colors, a metal backing film is formed by evaporation on the upper surface thereof, and the panel is baked to remove organic compounds from the phosphor film patterns and the film of acrylic resin, thereby forming a phosphor screen of the black matrix type.
According to such a conventional method of producing phosphor screens, however, the black matrix pattern is formed through lengthy steps consisting of panel washing--coating of the photoresist - exposure through shadow mask-developing--coating of light absorbing material-etching. Therefore, when the above method is adapted to form a phosphor screen of a superfine pitch tube that has been developed in recent years, minor defects that develop through the above-mentioned steps build up to deteriorate the quality of the phosphor screens as a whole and to decrease the production yield, making it difficult to meet the demand for the product.